Pumped storage power plant

ABSTRACT

Pumped-storage plant including a pump turbine, an electric motor-generator coupled with the pump turbine, an additional pump also coupled with the motor-generator, and means for admitting operating medium separately to the pump turbine and the additional pump, the additional pump having a construction for pumping only in an upper delivery head subrange ranging upwardly to maximum delivery head, and the pump turbine having a construction so that, when operating as a pump, it pumps only in a lower delivery head subrange ranging downwardly to minimum delivery head, both of the subranges being at least mutually adjacent, the pump turbine being further constructed so that, when operating as a turbine, it operates within the entire fall head range.

United States Patent Hutarew June 24, 1975 PUMPED STORAGE POWER PLANTPrimary Examiner-G. R. Simmons 75 inventor: Geor Hutarew Istuttgarbschoe'nberg, Germany Attorney, Agent, or FzrmHerbert L. Lerner[73] Assignee: J. M. Voith Gmbl-I, Heidenheim (Brenz), G ermany l5 7]ABSTRACT [22] Filed: Mar. 11, 1974 Pumped-storage plant including a pumpturbine, an

electric motor-generator coupled with the pump tur- [21] Appl. No.:450,222 bine, an additional pump also coupled with the motorgenerator,and means for admitting operating medium [30] Foreign ApplicationPriority Data separately to the pump turbine and the additional pump,the additional pump having a construction for Mar. l6, l973Germanymw..................... 2313095 pumping only in an upper deliveryhead Subrange D ranging upwardly to maximum delivery head, and the [52]US. Cl 290/52 X, 290/43 R, 417/374 pump turbine having a construction sothat, when ll'lt- Clt .2 erating as a p p it p p y in a lo er d i e yField of Search 417/374 35 290/52' head subrange ranging downwardly tominimum deliv- 290/44 53 ery head, both of the subranges being at leastmutually adjacent, the pump turbine being further constructed [56]References cued so that, when operating as a turbine, it operates withinUNITED STATES PATENTS the entire fall head range. 3,163,118 l2/l964Baumann.............................. 290/52 3.405.278 l0/l968 Ley290/52 7 Claims 3 Drawmg figures SHEET PATENTEIJ Jun 24 I975 Fig.2

Fig.3

1 PUMPED STORAGE POWER PLANT The invention relates to a pumped-storagepower plant, particularly, to a pumped-storage power plant for a widerange of fall heads and delivery heads, having a pump turbine providedwith adjustable guide vanes and coupled with an electricmotor-generator.

As is well known, for physical reasons the optimum for turbine and pumpoperation, both of which are at the same speed of rotation, occur atdifferrent fall and delivery heads for the two modes of operation. Inpumped-storage plants having a relatively wide operating range betweenthe maximum and minimum fall heads and between the maximum and minimumdelivery heads respectively, the following aggravating conditions occur.In both modes of operation, regions of the operating range haverelatively low effeciency must be taken into account; a condition whichis normally in the lower part of the fall and delivery head ranges. Thisis usually accompanied by an increase in the running instability orroughness. During turbine operation, the region characterized bypressure fluctuations in the suction pipe and detrimental secondaryphenomena related thereto becomes more pronounced and larger. But alsoduring pumping operation, increasing pressure fluctuations at theentrance to the guide vanes as well as to the rotor can be expected withincreasing distance from the optimum operating point because of flowseparation. But the most serious point is that during pumping operation,the cavitation behavior becomes more and more unfavorable withincreasing distance from the optimum operating point.

It is known that in order to avoid undesirable cavitation effects withrespect to possible destruction of material as well as with respect to adetrimental effect upon the characteristic curves, considerably lowerlevels for installation of the machine must be selected with increasingdelivery head range than with a smaller delivery head range in thevicinity of the optimum operating point. Primarily, however, thepressure-side cavitation at the rotor, which becomes more pronouncedwith decreasing delivery head or increasing output flow, would requireeconomically unfeasible extremely large feed heights or levels, in orderto avoid the attendant drop in efficiency and a shift on thecharacteristic curve toward the steep decline in the delivery head,which occurs beginning with a given region.

These phenomena, caused by physical process, generally apply toso-called conventional sets of machines formed of a pump and a turbine,as well as to machine sets with reversible pump turbines. In the lattercase, the following special conditions apply. Due to the relativeposition of the pump characteristic outside of or beyond the optimum ofthe performance diagram of the turbine, the aforedescribed unfavorableconditions of turbine operation are encountered even at a much smallerfall head range with decreasing fall head.

It is true that in a pump turbine with adjustable guide vanes, thepossibility exists to a certain degree, for the pumping operation, tolimit pump flow for decreasing delivery head by reducing the guide vaneaperture so that the installation depth' basically required, i.e,without adjustable guide vanes, can be reduced. However, the pumpcharacteristic is then shifted into a region of unfavorable efficiency.The detrimental effect during turbine operation, as compared with amachine set having a separate turbine, can in some cases be compensatedfor by selecting a lower speed for turbine operation than for pumpingoperation. This, however, results again in a large expenditure for theelectrical part of the plant and is unable to be realized advantageouslyin all rotary speed ranges.

It is an object of the invention to provide a pumpedstorage power plantwith a pump turbine which afiords coverage of a wide range of heads inboth modes of operation, but, however, have the power plant operateoutside unfavorable regions of the performance diagram with respect tocavitation behavior or efficiency, and avoid low, economicallyunjustifiable installation levels as well as the need for an electricmachine having two operating speeds.

With the foregoing and other objects in view, there is provided inaccordance with the invention a pumped storage power plant comprising apump turbine, an electric motor-generator coupled with the pump turbine,and an additional pump also coupled with the motor-generator, means foradmitting operating medium separately to the pump turbine and the pump,the additional pump being constructed for pumping only in an upperdelivery head subrange ranging upwardly to maximum delivery head, andthe pump turbine is so constructed that, when operating as a pump, itpumps only in a lower delivery head subrange ranging downwardly tominimum delivery head, both of the subranges being at least mutuallyadjacent, the pump turbine being further so constructed that as aturbine, it operated within the entire fall head range. The pump turbineis thus constructed advantageously so that maximum delivery head islocated in the region of the optimum of the turbine performance diagram,and preferably somewhat below the optimum normalized speed.

in this manner, there is obtained a pumped-storage plant with a widefall and delivery head range which operates economically druing turbineoperation as well as during pumping operation thereof with goodefficiency and, particularly during pumping operation thereof, largelyavoiding regions wherein there is danger of cavitation.

A pumped-storage plant having a pump turbine and an additional pump forcontrolling large fall and delivery heads has, in fact, become knownheretofore, wherein both machines are used simultaneously in series forpumping operation (note the article in Hydraulische Maschinen filrPumpspeicheranlagen..." by E. H. Muehlemann in Escher-Wyss-Mitteilugenl972/l. p. 3 to 11, particulary FIG. 6, p.6). Each machine of thisheretofore known assembly takes over part of the total delivery head.Such an installation, however, is not suited for controlling a largedelivery head range, because the same detrimental operational conditionsdescribed hereinabove would occur therein. This known assemblyfurthermore requires a separate starting turbine whereas, in aninstallation according to the invention of the instant application, aseparate starting turbine can be dispensed with if, in accordance with apreferred embodiment of the invention, during operation as a turbine,the additional pump is operated with the same direction of rotation asthe pump turbine. Then, the pump can be accelerated with the pumpturbine which operates as a turbine, and the pump can be used as astart-up turbine for the pump turbine in the direction of rotation ofthe pump. Although the latter procedure is used only in the lower fallhead range, wherein the pump functioning as a turbine operates in arelatively unfavorable operating range, this will in most cases bepossible down to the minimum fall head because, on the one hand, thenomi-' nal pump output of the pump turbine is lower than that of thepump and, on the other hand, when starting up, maximally only about 25%of the nominal power is required against the closed guide vanes when thenorminal rotary speed has been reached.

Other features considered as characteristic for the invention are setforth in the appended claims.

Although the invention is illustratsd and described herein as embodiedin a pumped-storage power plant, it is nevertheless not intended to belimited to the details shown, since various modifications and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings, in which:

FIG. I is a performance graph or diagram of the machines of apumped-storage power plant constructed in accordance with the inventionof the instant application; and

FIGS. 2 and 3 are diagrammatic views of two different embodiments of thepumped-storage power plant of the invention showing varying assembliesof the machines thereof.

Referring now to the drawing and first, particularly, to the diagram orgraph of FIG. I, normalized speeds n,'/n,,,,,,' referred to therespective optimal value, are plotted along the abscissa increasing fromthe left to the right-hand side of the figure, and values H/I-I,,,,, ofthe fall or delivery head, also referred to the respective optimumvalue, are plotted along the abscissa increasing from the right to theleft-hand side of the figure along the ordinate at the left-hand side ofFIG. 1, normalized water flow 0.70mi. again referred to the optimalvalue is plotted. In the diagram of FIG. 1 there is also plotted forturbine operation the efficiency curves M or so-called shell curves,"and the curves of different guide vane aperture alu as well as the pumpcharacteristic curve Pu for pump operation of the pump turbine. Forbetter understanding, the curves of the cavitation coefficients 0' andthe efficiencies 0', for pump operation of the pump turbine, as afunction of Q,'/Q,,,,,', are added at the right-hand side of FIG. 1.

The operational behavior of a heretofore known pumped-storage plant withonly a pump turbine will be explained first with the aid of the diagramor graph of FIG. 1. For this purpose, the maximum and minimum fall ordelivery head H and H shown by the dotdash lines in the diagram of FIG.1, are given for the relatively large operating range F in order tosimplify the presentation, the pipeline losses have not been taken intoconsideration. It is known that during turbine operation, this range F,is outside the optimal point 1,117 I; it is still relatively close tothis point for the maximum fall head H but even with the guide vanesfully open, a/a I, it is below n11 0.7 for the minimum fall head H Forthe pumping operation, it will be seen from the diagram of FIG. 1 thatunfavorable cavitation coefficients 0 and efficiencies 1;, are obtainedin the lower delivery head subrange, as previously explainedhereinabove. In the diagram example of FIG. I, these unfavorable valuesare above about Q 'lQ 1.4.

The situation is completely different, however, when the pumped-storageplant is constructed in accordance with the invention of the instantapplication. The fall and delivery head range F for this case isrepresented by respective dash-dot-dot-dash lines in the diagram of FIG.1 for I-l and H It will be readily seen that the optimal point 11/11,, lis fully encompassed with the range F for turbine operation and is nearH Rather favorable values for the efficiency are also yet obtained for HFor pump operation, the range of delivery heads F is divided into twosubranges F and F The pump turbine can be used for pump operation, ofcourse, only in the lower fall head range F down to H The upper limit ofthis range is located at about the value H of the first example of aplant with only a pump turbine. The 1;, and 0- values obtained the rangeF at the level of the intersection of H with the pump characteristiccurve Pu are considerably more favorable than in the first casediscussed hereinabove. The adjacent upper subrange F is taken over bythe additional pump alone of the invention of this application, whichcan be constructed specifically for this delivery head subrange. The twopump subranges should be divided so that a certain amount of overlap isobtained and so that overall, optimum efficiency and the least possibleinstallation levels can be achieved.

In FIG. 2, one embodiment of an installation according to the inventionhaving a horizontal shaft 4 is shown. The motor-generator 7 is locatedbetween the pump turbine 5 and the additional pump 6. Whichever machine5 or 6 is not in use is vented. The pumpturbine 5 is provided withconventional adjustable guide vanes.

In the embodiment of a set of machines having a vertical shaft 8according to FIG. 3, that hydraulic machine which requires the greaterfeed height should be in the lower position, if possible. In theembodiment of FIG. 3, the pump turbine 5 is constructed for a greaterfeed head, because it is advantageous that the suction pipe 9 of thepump turbine 5 be not penetrated by the shaft 8 and, in consideration ofthe turbine operation, a sufficient axial extension of the suction elbowshould be realized. In the embodiment of FIG. 3, the pump 6 is disposedimmediately above the pump turbine 5. However, it is also possible tolocate the pump 6 above the motor-generator 7 with the suction elbowextending upwardly.

I claim:

1. Pumped-storage plant comprising a pump turbine, an electricmotor-generator coupled with said pump turbine, an additional pump alsocoupled with said motor-generator, and means for admitting operatingmedium separately to said pump turbine and said additional pump, saidadditional pump having a construction for pumping only in an upperdelivery head subrange ranging upwardly to maximum delivery head, andsaid pump turbine having a construction so that, when operating as apump, it pumps only in a lower delivery head subrange ranging downwardlyto minimum delivery head, both of said subranges being at leastrnutually adjacent, said pump turbine being further constructed so that,when operating as a turbine, it operates within the entire fall headrange.

5. Pumped-storage plant according to claim I wherein said additionalpump is actuable as a starting turbine for starting up said pump turbinein the pumping mode of operation thereof.

6. Pumped-storage plant according to claim 1 wherein said pump turbinehas adjustable guide vanes.

7. Pumped-storage plant according to claim 5 wherein said pump has guidevanes which are adjustable to form a wider aperture therebetween thanrequired for normal pump operation.

1. Pumped-storage plant comprising a pump turbine, an electricmotor-generator coupled with said pump turbine, an additional pump alsocoupled with said motor-generator, and means for admitting operatingmedium separately to said pump turbine and said additional pump, saidadditional pump having a construction for pumping only in an upperdelivery head subrange ranging upwardly to maximum delivery head, andsaid pump turbine having a construction so that, when operating as apump, it pumps only in a lower delivery head subrange ranging downwardlyto minimum delivery head, both of said subranges being at least mutuallyadjacent, said pump turbine being further constructed so that, whenoperating as a turbine, it operates within the entire fall head range.2. Pumped-storage plant according to claim 1 wherein said pump turbineis constructed so that said maximum fall head is located in a region ofoptimal performance in a performance diagram of the turbine made of saidpump turbine.
 3. Pumped-storage plant according to claim 2 wherein saidmaximum fall head is located below optimum normalized speed. 4.Pumped-storage plant according to claim 1 wherein said additional pumphas a direction of rotation which is the same as that of said pumpturbine in the turbine mode of operation tHereof.
 5. Pumped-storageplant according to claim 1 wherein said additional pump is actuable as astarting turbine for starting up said pump turbine in the pumping modeof operation thereof.
 6. Pumped-storage plant according to claim 1wherein said pump turbine has adjustable guide vanes.
 7. Pumped-storageplant according to claim 5 wherein said pump has guide vanes which areadjustable to form a wider aperture therebetween than required fornormal pump operation.